An exemplary embodiment relates to mechanical latching structures, and more particularly to latching springs for an electrical interconnect.
In the related art, there are various interconnecting devices. For example, U.S. Pat. No. 6,439,898 discloses a method and apparatus for interconnecting at least two devices using an adhesive. In the related art, solder is used for electrical interconnects. In multi-chip microelectronic assemblies, solder interconnects are subject to damage and misregistration caused by heating the assembly to solder it to a substrate or circuit boars. In addition, solder typically contains lead. There is a trend in the industry to get away from using toxic substances such as lead. Thus, solder that contains silver is used as a replacement for lead solder. However, silver solder is more expensive and requires a higher temperature for processing than lead solder.
As an alternative to solder, the use of a cantilever spring, for example, with a fastening mechanism, is used to hold the interconnect together and maintain spring contact pressure. However, such a spring provides only a single point contact. A single point contact, without solder, can lead to electrical glitches when the contact moves. For example, U.S. Pat. No. 6,555,415 discloses an electronic configuration having a first surface with electrical contacts for electrical bonding. This electronic configuration requires the use of a bump for electrical bonding to form one contact.
Furthermore, conventional bent cantilever springs pop off their mating pads unless a fastening mechanism is used to hold the parts together and maintain spring contact pressure. Currently, electronic package parts are assembled using either solder to form a permanent metal joint at the spring tip or an adhesive to join a chip to the substrate. When using spring devices, the spring is either maintained under compression or a solder joint is placed at the tip of the spring. Whether the parts are assembled using solder, adhesives, or compression, they all still lack the ability for reworkability. That is, it would be difficult to detach then reattach the assembled parts for re-use.
Although a soldered part may be reworked, such would require heating the connector to melt the solder in order to disengage the attached parts. Further, some adhesives are not at all reworkable. Furthermore, once there is, for example, injection molding around a part, it can be very difficult to rework. In addition, solder free connections are highly desirable both for the elimination of lead as well as for the ability to eliminate the temperature cycle needed for reflow, and for the ability to replace individual parts of the connection.
Furthermore, interconnecting devices are a primary consideration in electronic components for high volume applications. This is particularly important in interconnection components. Another consideration is the complex process of fabrication, which entails added cost. Accordingly, a process for fabricating compliant spring contacts that is simple and that can fit in existing infrastructure is needed to simplify manufacturing and reduce cost.
Accordingly, a spring contact that mates and latches is desired. Further, a compact means of introducing multiple contact points is desired. Still further, a latching mechanism that can be disassembled is desired. With such a latching spring, parts may be engaged together and then separated, without the need for increased temperature, on several occasions, as need be, before any degradation of the contacts involved occurs.
Accordingly, there is a need for latching springs with redundant contact points for solder free electrical connection of devices. There is also a need for an interconnection designed to function through a series of connect-disconnect cycles. Furthermore, there is a need for a method for providing latching springs that is cost effective.